Ask Your Question

Negative values for y-coordinates after Triangulation

asked 2018-01-11 20:33:50 -0500

malharjajoo gravatar image

updated 2018-01-12 02:10:52 -0500

LBerger gravatar image


I have been able to implement a basic version of triangulation ( using SIFT detector for stereo correspondence problem ) I have also noticed that the triangulation gives a poor result if the SIFT detector matches non-corresponding or incorrect feature points. However, as seen in images below, the SIFT detector seems to be doing a good job for the given frame. However the triangulation doesn't seem to work out.

Kindly see images below for a given stereo camera setup-

1) Stereo Correspondence (for left and right camera images): C:\fakepath\feature_matches.png

2) Triangulation (only shown in left camera image->):C:\fakepath\Triangulation.jpg

Clearly, the y-coordinate is negative while values of x and z-coordinate for short distances seem "reasonable" (given that I have a rms re-projection error = 0.87 after calibration, which I'm aware needs to be improved).

My Question:

1) Is the camera pinhole model in openCV actually having the y-axis inverted ?

2) Is this a standard result of triangulation using openCV, ie having negative y-values ?

Any help would be greatly appreciated.

edit retag flag offensive close merge delete


I was wondering the same thing but thanks for confirming that from the docs. If you can write this down as the answer instead of a comment, I will mark it as the answer.

malharjajoo gravatar imagemalharjajoo ( 2018-01-12 11:34:41 -0500 )edit

1 answer

Sort by ยป oldest newest most voted

answered 2018-01-12 02:18:10 -0500

LBerger gravatar image

Coordinate system is described here. z values must be positive. x and y can be negative or positive because system origin is optical center of left camera

edit flag offensive delete link more

Question Tools

1 follower


Asked: 2018-01-11 20:33:50 -0500

Seen: 1,725 times

Last updated: Jan 12 '18